Method and apparatus for feeding high speed presses

ABSTRACT

This invention is addressed to a new and improved method for automatic precision feeding of high speed presses for mechanically working metal strips in which the metal strip is fed to the press in a precise longitudinal position relative to the die stamp with recovery of elongation due to the effect of the die stamp wherein the strip is gripped between the jaws of at least two movable grips, one above the press and the other below the press in the direction through which the strip is advanced, whereby the movable grips are displaced to advance the strip and the strip is then gripped by at least two fixed grips, one above and another below the press, while the movable grips are displaced to their starting position in which the fixed grips below the press open before the movable grips close while the fixed grip above the press opens as the movable grips have closed to permit recovery of the elongation of the strip.

Laurencin Jan. 9, 1973 METHOD AND APPARATUS FOR FEEDING HIGH SPEED PRESSES Marcel Laurencin, Castelsarrasin, France Assignee: Cegedur GP, Paris, France Filed: Oct. 9, 1970 Appl. No.: 79,494

Inventor:

Foreign Application Priority Data Oct. 16, 1969 France ..6935463 US. Cl ..72/421, 72/422 Int. Cl ..B21d 43/02, B21d 43/10 Field of Search ..72/422, 421, 252; 226/141, 226/142, 162; 83/277 References Cited UNITED STATES PATENTS 3/1964 Olson ..226/162 11/1968 Roch ..83/277 10/1969 Butler ..226/l42 Primary Examiner-Charles W. Lanham Assistant Examiner-R. M. Rogers Attorney-McDougall, Hersh & Scott [57] ABSTRACT This invention is addressed to a new and improved method for automatic precision feeding of high speed presses for mechanically working metal strips in which the metal strip is fed to the press in a precise longitudinal position relative to the die stamp with recovery of elongation due to the effect of the die stamp wherein the strip is gripped between the jaws of at least two movable grips, one above the press and the other below the press in the direction through which the strip is advanced, whereby the movable grips are displaced to advance the strip and the strip is then gripped by at least two fixed grips, one above and another below the press, while the movable grips are displaced to their starting position in which the fixed grips below the press open before the movable grips close while the fixed grip above the press opens as the movable grips have closed to permit recovery of the elongation of the strip.

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METHOD AND APPARATUS FOR FEEDING HIGH SPEED PRESSES This invention relates to a method for the automatic high precision feeding of high speed presses, and to a machine by which this process is carried out.

The invention is intended for application in forming presses.

More particularly, the invention is applicable to high speed precision cutting, dieing and extrusion presses by which it is possible to obtain such components as optionally holed blanks intended, for example, for ram extrusion, dishes with highly accurate diminsions, from strip and, more particularly, from rolled strip or sheet billets by cutting, optionally accompanied by stamping, dieing or extrusion. By virtue of the invention, it is possible to work any materials, including those with poor mechanical properties, such as aluminum, lead zinc and plastics.

A feeding machine should enable the strip to be worked to be positioned with precision beneath the die stamp of the press both in the longitudinal direction while ensuring a rate of advance equal to the required advance rate after each pressing stroke, and in the transverse direction.

There are already excellent presses for cutting metals of high mechanical strength, but none of these conventional presses is satisfactory in regard to the cutting of materials with poor mechanical strength.

It is known that washers with a hole in the middle can be cut in two operations. A first die stamp of limited cross-section first cuts the central hole, while a second die stamp of greater cross-section separates the washer. The second die stamp comprises, in an extension of the tool, a so-called pilot element whose cross-section is very slightly smaller than that of the first die stamp which, by engaging in the central hole initially cut, enables the strip to be correctly positioned by rectifying the rate of advance of the feeding machine. The strip is advanced either by two pressure rollers which grip the strip above or below the press, the strip being released by lifting the upper rollers during engagement of the pilot of the second die stamp, or by two grippers one of which is movable and grips the strip during a downward translatory movement, while the other is fixed and grips the strip during the return movement of the open movable gripper.

This technique can only be applied to brittle materials because the pilot would deform the hole formed by the first die stamp instead of rectifying the rate of advance.

It is also known that the feed mechanism can be regulated in such a way that it advances the strip by a distance slightly greater than the required advance rate, and that two trimming blades or tools which cut the edges of the strip can be arranged along the edges, the feed mechanism being stopped when these trimming blades have cut a length exactly equal to the required rate of advance.

This method is used for brittle materials, but it does have the serious disadvantage of causing losses of starting material and of requiring expensive machinery.

The machine comprising movable and fixed grippers referred to above has also been improved to obtain greater precision. The movable gripper moves between two stops which determine the length of the advance stroke. The gripper can be controlled mechanically from the crankshaft of the press, or pneumatically, in which case a first distributor feeds the fixed and movable grippers while a second distributor feeds a jack driving the 'movable gripper, a cam mounted on the crankshaft actuating a flap by which the cycle is initiated. Positioning is ensured by trimming blades.

This machine works at a slow rate and only functions properly where the strips have relatively small crosssections and, above all, thicknesses.

Finally, in another known arrangement, the translatory movement of the movable gripper is produced by a mechanism comprising a crank keyed to the crankshaft of the press which, through a lever provided with a toothed sector and a pinion, acts on an oscillating shaft which controls the movable gripper through a second lever. Synchronized with this mechanism for displacing the strip there is a hydraulic system by which the grippers are closed, their release being effected by springs in the absence of hydraulic pressure. The jacks of the grippers are fed by one of the two lateral guides of the movable grippers, or through distributors and flexible hoses. The fixed grippers are opened through ramps arranged laterally of the slide block of the press acting on two rollers supported by two levers integral with movable jaws.

The disadvantage of this arrangement is that it does not take into account the elongation of the strip or sheet billet under the effect of the die stamps. Thus, a strip of aluminum measuring 78 X 12 millimeters was found to undergo 250 mm. elongation after 26 perforations 66 mm. in diameter. This disadvantage which is common to all the conventional machines only affects brittle materials and is unacceptable.

It is accordingly an object of this invention to provide a method for the automatic precision feeding of high speed presses by means of which the strip feeding the press can be precisely positioned in relation to the die.

stamps of the press with recovery of the elongation due to the action of the die stamps.

It is a related object of the invention to provide a machine by which this method is carried out.

These and other objects and advantages of the invention will appear more fully hereinafter, and, for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings in which:

FIG. 1 is a view showing the various components of a cutting press and its accessories;

FIG. 2 is a section through a movable or fixed gripper;

FIG. 3 is a perspective view showing a first example of the feed mechanism;

FIG. 4 is a plan view of part of this mechanism;

FIGS. 5, 6 and 7 are sections through FIG. 4 on the lines a, b, and c respectively;

FIG. 8 is a perspective diagram showing a second example of the feeding machine;

FIG. 9 is the strain diagram of a feeding machine of the type shown in FIG. 3 or FIG. 8; and,

FIG. 10 is a plan view of a press platform equipped with a roller guide mechanism.

In the method according to the invention, the strip is advanced by gripping it between the jaws of two movable grippers; one arranged above and the other below vanced, a downward translatory movement is imparted to these two grippers, the strip is then gripped between the jaws of two fixed grippers, one arranged above and the other below the press, while the movable grips are opened and, through an upward translatory movement, are returned to their starting position, the movements of the two movable grips being identical and in phase with one another. .The method according to the invention is distinguished by the fact that the lower fixed gripper opens before the movable grips close while the upper fixed gripper only opens after they have closed, andon the other hand by the fact that one of the edges of the strip is pressed resiliently against lateral stops which act as position references in the transverse direction.

The machine according to the invention comprises a strip feed mechanism consisting of two pairs of grippers which are closed, preferably hydraulically, through distributors and opened by strings of the return kind, one upper pair and one lower pair, each pair comprising one fixed grip and one movable grip mounted on a sliding grip-supporting carriage, the two upper and lower movable grippers being joined together. The machine according to the invention is distinguished by the fact that the distributors of the fixed grippers are controlled by cams in turn controlled by the crankshaft of the press, the cam actuating the distributor of the upper grip being offset downwards relative to the cam of the lower grip in such a way that the lower fixed grip opens before the movable grips have opened while the upper fixed grip opens after the movable grips are closed to allow recovery of the elongation of the strip under the effect of the die stamps of the press, and on the other hand by at least two rollers each designed to rotate about an axle integral with the press, these rollers being situated along one of the edges of the strip, at least two rollers each designed to rotate about an axle and elastic means by which these axles are returned in the direction of the fixed axles. I

By virtue of the machine for automatically feeding high speed precision presses, it is possible to obtain components with precision dimensions both at a high rate and with a very small number of rejects, from sheet billets, i.e., a very fiat and long semi-finished product, or strip rolled from a material even with poor characteristics by cutting, optionally accompanied by stampmg.

The, press is of any known type and does not form part of the invention, although the feed mechanism is controlled by its crankshaft l.

The arrangement enables strips of a brittle material to be cut in the press with a limited distance, equal to about half the thickness of the strip, between holes because it takes into account the elongation of the strip under the effect of the cutting die stamp.

The stripadvance mechanism comprises two sets of two grips, one set at the inlet end(front grips) and the other at the outlet end. Each set of grips comprises one movable grip providing for the translatory movement of the strip and one fixed grip which holds the strip during the return stroke of the movable grip. Each movable grip is mounted on a sliding grip-supporting carriage, this sliding movement being controlled mechanically from the crankshaft of the press. The displacement of the carriages is strictly related to their rotation. A kinematic damping system with a stationary phase at the ends of the stroke of the sliding carriages is provided. The movements of the front and rear carriages are strictly identical and in phase with one another.

Each grip, fixed or movable, is hydraulically tightened and mechanically or pneumatically released. The response time for tightening and release of the jaws is around 0.01 second in relation to the information given by the position of the crankshaft of the press.

Consistent with the position of the crankshaft; the

tightening and release cycles of the front and reargrips strip Q coming from the roll D enters the front movable and fixed grips AM and AF, respectively, after which it passes into the press P whose die stamp Pa cuts and optionally stamps the components to be obtained, and finally into the rear fixed and movable. grips BF and BM, respectively, before being taken up by the winding mechanism E.

The four grips can be identical and of the type shown in FIG. 2. The grip denoted by the general reference 4 comprises a fixed jaw 41 whose position can be adjusted by means of a screw 411 operated by .a handwheel 412, and a movable jaw 42 controlled by a hydraulic or pheumatic jack 43 whose piston 431 is integral with the jaw and whose cylinder 432 is accommodated in the casing 45 of the gripper. The movable gripper is thrust in the opening direction by springs 44. This gripper is closed by applying pressure to the jack 43 and opened by the pressure of the springs 44. As can be appreciated by those skilled in the art, the springs can be replaced by a pneumatic or hydraulic member.

The mechanism by which the movable grips are displacedcan be made in accordance with two examples described below, the drive shaftbeing formed in both cases by the crankshaft 1 of the press P.

In a first embodiment shown 'in FIGS. 3 to 7, the a drive shaft 1 acts through two conical pinions 11 and 12 of the precision-cut type on an intermediate shaft 13 coupled through a homokinetic joint 16 to a vertical shaft 17 held on its axis or rotation by ball bearings 14 and 15.

Keyed on the intermediate shaft 13 there is on the one hand a cam 22 and on the other hand a contactor 29 rotatable in five directions by which the hydraulic grips 4 are tightened. The cam 22 rotates in a horizontal plane about the axis of the shaft 17 causing the alternate displacement of a false sliding carriage 26 mounted on roller slides 261 and 262.

To ensure that the movement of the flase carriage 26 remains strictly related to the profile of the cam 22, the false carriage carries two rollers diametrically opposite in relation to the axis of the shaft 17, namely a first roller 23 whose spindle is integral with the false carriage, and a second roller 24 kept constantly in contact with the cam by an elastic means such as a stack of elastic washers 25.

The profile of the cam is determined in such a way that the alternate movement of the false carriage is kinematically damped, in other words it comprises a uniformly accelerated movement followed by a stationary zone preceding a uniformly retarded movement which in turn is followed by another stationary zone.

A lever 27 oscillating about a point 28 transmits the movement of the flase carriage 26 to a displaceable grip-supporting carriage 31 through two spindles 32 and 33 and a rod 34, the spindle 33 performing the function of a safety spindle which is cut in the event of overloading of the displaceable grip-supporting carriage 31.

The pivot point 28 can be mounted on an intermediate carriage 281 designed to slide on command. In this way, it is possible to vary the position of the pivot 28 in relation to the ends of the rod 27. Accordingly, by modifying the ratio of the lever arms, it is possible to vary the amplitude of the displacement of the movable grip-supporting carriage 31. The displacement of the pivot 28 can be controlled by a mechanism comprising a screw 282 and a nut 283 controlled by a sliding gauge.

The grip-supporting sliding carriage 31 can slide on roller slides 311 and 312.

As front and rear grips are used, each movable grip is mounted on a separate carriage, the two carriages being coupled together by two lateral connecting rods.

The arrangement operates as follows: the intermediate shaft 13 and the joint 16, through conical pinions 11-12, the crank-shaft 1 acts on the vertical shaft 17 which, in turn, rotates the cam 22. The cam 22, presses against the roller 23 by the roller 24, imparts to the false carriage 26 a reciprocating movement strictly related to the profile of the cam, this movement being kept straight by means of roller slides 261 and 262. Through the rod 27 rocking about the pivot 28 and the link 34, the false carriage 34 drives the carriage 31 which carries one of the movable grips.

Simultaneously, the rotary contactor 29 keyed to the vertical shaft 17 acts on electrical contacts through which are fed hydraulic distributors controlling the jacks of the fixed and movable grips. The electrical contacts can be replaced by proximity detectors.

The keying of the cam and the contactor 29 to the shaft 17 and the regulation of the position of the pivot 28 by acting on the screw 282 controlling the intermediate carriage 281 make it possible to obtain an operation according to the diagram shown in FIG. 9.

In a second embodiment shown in FIG. 8, the crankshaft 1 of the press carries on the one hand an end crank 51 which controls the alternate translatory movement of the sliding grip-supporting carriage 31, and on the other hand two helical pinions 61 and 62 controlling the opening and closing of the grips.

Through a link 52, the crankshaft 51 controls a toothed segment 53 pivoting about a spindle 531. This toothed segment acts on a pinion 541 keyed to an oscillating shaft 54 to which there is also keyed a crank 542 whose pitch can be regulated by means of the screw 543 and the nut 544. Through a link 55, the crank 542 acts at 563 on a lever 56 designed to oscillate about a spindle 561. At its upper end, this lever is pivoted at 562 to the carriage 31 which carries the front or rear movable grip 4. At its lower end, it is pivoted at 564 to a rod 57 which controls an identical lever pivoted at its upper end to the carriage which carries the other front or rear movable grip.

The helical pinion 62 is keyed to a vertical shaft 63 which through another two helical pinions 64 and 65 acts on a horizontal satellite shaft 66 which through two cams 67 controls the opening of the fixed grippers by acting on the distributors feeding the jacks 43 of these grippers and, through two rotary distributors 68, controls the opening of the movable grippers, the rotary distributors feeding the facks 43.

The mode of operation of this arrangement is as follows. Through the crank 51, the link 52 and the toothed segment 53, rotation of the crankshaft 1 drives the pinion 541 which makes the shaft 54 oscillate. The crank 542 thus has imparted to it a reciprocating movement whose stroke can be regulated by acting on the head of the screw 543. The lever 56 receives a similar movement, driving the carriage 31 which carries one of the movable grippers. Through the link 57, the lever 56 drives an identical lever which in turn drives the carriage carrying the other gripper. Through the pinions 61-62, the vertical shaft 63 and the pinions 64-65, rotation of the crankshaft 1 also rotates the horizontal shaft 66. This shaft 66 drives cams 67 controlling the distributors of the fixed grippers and the rotary distributors 68 acting directly upon the movable grippers. The keying of the cams 67 and the distributors 68 to the shaft 66, the keying of the crank 51 to the crankshaft 1 and regulation of the screw 543 make it possible to obtain an operation according to the graph shown in FIG. 9.

Omission of the trimming blades makes it necessary for the strip to be laterally guided. To this end, the platform of the press is provided with stops. In the embodiment shown in FIG. 1, the stops are formed by two rollers 71 and 72 designed to rotate about spindles 711 and 721, respectively, integral with the platform, and the press comprises another two rollers 73 and 74 whose axles are urged in the direction of the fixed axles 711 and 721, respectively, by springs 732 and 742, respectively. The chain-dot line bearing the reference forms the reference line for the lateral guiding of the strip which the rollers 73 and 74 press against the rollers 71 and 72. At the center of the figure there can be seen small diameter punches for forming a central hole, and cutters of large diameter for cutting studs manufactured by the press whose platform is shown and, in the top left-hand corner and bottom right-hand corner of the figure, the two columns along which slide the die holders (not shown). The arrow 700 indicates the direction in which the strip is unwound.

By way of illustration, the invention feeds a press by which it is possible to cut holed studs between 2.5 and I6 mm thick, the rate at which the strip is unrolled being adjustable between 2 and 18 meters per minute and the work rate between 75 and 300 strokes per minute. The tolerances on the inner and outer diameters are i 0.03 and i 0.04 mm., respectively, the maximum eccentricity of the central hole not exceeding 0.04 mm. The proportion of reject studs only amounts to l in 1 million. The tightening pressure on the grips is independent of the thickness of the strip and the stroke rate.

It will be apparent that various changes and modifications can be made in the details of construction,

procedure and use without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. A method for the automatic precision feeding of high speed presses for mechanically working a metal strip which enables the strip fed to the press to be placed in a precise longitudinal position relative to the die stamps of the press with recovery of the elongation due to the effect of the die stamps comprising gripping the strip between the jaws of at least two movable grips, one of which is situated above and the other which is situated below the press in a direction through which the strip is advanced, displacing the movable grips to advance the strip, gripping the strip between the jaws of at least two fixed grips, one above the press and another below the press in the direction in which the strip is advanced, while the movable grips are displaced to their'starting position, with the movement of each of themovable grips being the same and in phase each with .the other wherein the fixed grip below the press opens before the movable grips close while the fixed grip above thedpress opens after the movable grips have closed.

2.A method as defined in claim 1 wherein each grip is closed hydraulically.

3. A strip feed mechanism for the automatic precision feeding ofa high speed press comprising at least a pair of movable grips, one of the gripsbeing positioned in front of the press and the other behind the press, said movable grips being movable along a longitudinal direction, at least a pair of fixed grips, one .of the grips being positioned in front of the press and the other behind the press and means controlled by the crankshaft of the press to simultaneously displace said movable grips to advance the movable grips while engaged with the strip, said means including means to open the fixed grip behind the press before the movable grips close to engage the strip while the fixed grip in front of the press is opened after the movable grips close to permit recovery of the elongation of they strip.

4. A mechanism as defined in claim 3 wherein each of the movable grips is fixed on a sliding carriage, with each of the grips being connected whereby the displacement of the movable grips are the'same and in phase each with the other in response to rotation of the crankshaft.

5. A mechanism as defined in claim 3 which includes hydraulic means to open each of the grips and spring means to close the grips.

6. A mechanism as defined in claim 4-which includes cam means to displace each of said movable grips and to actuate the opening and closing of each of said grips in response to the crankshaft.

7. A mechanism as defined in claim 6 which includes a pair of rollers adjacent to said cam means whereby displacement of each of the carriages corresponds to the profile of said cam means. 

1. A method for the automatic precision feeding of high speed presses for mechanically working a metal strip which enables the strip fed to the press to be placed in a precise longitudinal position relative to the die stamps of the press with recovery of the elongation due to the effect of the die stamps comprising gripping the strip between the jaws of at least two movable grips, one of which is situated above and the other which is situated below the press in a direction through which the strip is advanced, displacing the movable grips to advance the strip, gripping the strip between the jaws of at least two fixed grips, one above the press and another below the press in the direction in which the strip is advanced, while the movable grips are displaced to their starting position, with the movement of each of the movable grips being the same and in phase each with the other wherein the fixed grip below the press opens before the movable grips close while the fixed grip above the press opens after the movable grips have closed.
 2. A method as defined in claim 1 wherein each grip is closed hydraulically.
 3. A strip feed mechanism for the automatic precision feeding of a high speed press comprising at least a pair of movable grips, one of the grips being positioned in front of the press and the other behind the press, said movable grips being movable along a longitudinal direction, at least a pair of fixed grips, one of the grips being positioned in front of the press and the other behind the press and means controlled by the crankshaft of the press to simultaneously displace said movable grips to advance the movable grips while engaged with the strip, said means including means to open the fixed grip behind the press before the movable grips close to engage the strip while the fixed grip in front of the press is opened after the movable grips close to permit recovery of the elongation of the strip.
 4. A mechanism as defined in claim 3 wherein each of the movable grips is fixed on a sliding carriage, with each of the grips being connected whereby the displacement of the movable grips are the same and in phase each with the other in response to rotation of the crankshaft.
 5. A mechanism as defined in claim 3 which includes hydraulic Means to open each of the grips and spring means to close the grips.
 6. A mechanism as defined in claim 4 which includes cam means to displace each of said movable grips and to actuate the opening and closing of each of said grips in response to the crankshaft.
 7. A mechanism as defined in claim 6 which includes a pair of rollers adjacent to said cam means whereby displacement of each of the carriages corresponds to the profile of said cam means. 